Dicalcium phosphate is the calcium phosphate with the formula CaHPO4 and its dihydrate. The "di" prefix in the common name arises because the formation of the HPO42– anion involves the removal of two protons from phosphoric acid, H3PO4. It is also known as dibasic calcium phosphate or calcium monohydrogen phosphate. Dicalcium phosphate is used as a food additive, and it is found in some toothpastes as a polishing agent and biomaterial.[1][2] Preparation Dibasic calcium phosphate is produced by neutralizing calcium hydroxide with phosphoric acid, precipitating the dihydrate as a solid. At 60 °C the anhydrous form is precipitated:[3] H3PO4 + Ca(OH)2 → CaHPO4 +2H2O To prevent degradation that would form hydroxyapatite, sodium pyrophosphate or trimagnesium phosphate octahydrate are added when, for example, dibasic calcium phosphate dihydrate is to be used as a polishing agent in toothpaste.[1] In a continuous process CaCl2 can be treated with (NH4)2HPO4 to form the dihydrate: CaCl2 + (NH4)2HPO4 → CaHPO4•2H2O + 2NH4Cl A slurry of the dihydrate is then heated to around 65–70 °C to form anhydrous CaHPO4 as a crystalline precipitate, typically as flat diamondoid crystals, which are suitable for further processing.[citation needed] Dibasic calcium phosphate dihydrate is formed in "brushite" calcium phosphate cements (CPC's), which have medical applications. An example of the overall setting reaction in the formation of "β-TCP/MCPM" (β-tricalcium phosphate/monocalcium phosphate) calcium phosphate cements is:[4]